When an ideal capacitor is charged by a dc battery, no current flows. However, when an ac source is used, the current flows continuously. How does one explain this, based on the concept of displacement current ? [Delhi I, II, III 2012]
When an ideal capacitor is charged by a dc battery, the charge flows (momentarily) till the capacitor gets fully charged. When an ac source
is connected, then conduction current
{ i }_{ c }=\frac { dq }{ dt }
keeps on flowing in the connecting wires.
Due to the changing current, the charge deposited on the plates of the capacitor changes with time. This causes change in electric field between the plates of the capacitor which causes the electric flux to change and gives rise to a displacement current in the region between the plates of the capacitor.
and is equal to the conduction current at all instants.